There has been conventionally developed a solid-state electronic device including a ferroelectric thin film that possibly enables high speed operation. Metal oxide has been developed popularly as a dielectric material for a solid-state electronic device. Examples of dielectric ceramics that does not contain Pb and can be baked at a relatively low temperature include BiNbO4. There is a report on dielectric properties of such BiNbO4 formed in accordance with the solid phase epitaxy (Non-Patent Document 1). The applicant of this application has filed, although not yet being laid open, inventions relating to an oxide layer and a manufacturing method thereof (Patent Documents 1 and 2). The oxide layer (possibly including inevitable impurities) consists of bismuth (Bi) and niobium (Nb) and includes a crystal phase of a certain special crystal structure. The oxide layer enables simplification in manufacturing step and has comparatively high insulation and relative permittivity.